The human eye includes a flexible lens that focuses incoming light onto the retina. When the incoming light does not focus properly on a person's retina, the person's vision is blurry or otherwise impaired. For example, people with nearsightedness (myopia) or farsightedness (hyperopia) cannot focus on distant or nearby objects, respectively. These conditions may be treated with corrective lenses such as eyeglasses or contact lenses.
Many people progressively lose their ability to focus on nearby objects as they age, a condition known as presbyopia. This condition may also be treated with corrective lenses such as eyeglasses or contact lenses. People who also require correction for distance vision may use static multi-focal lenses such as bifocals, trifocals, or progressive lenses. Those solutions provide different levels of vision correction for different parts of the lens. Thus, for close vision the user is required to adjust his or her viewing angle, head position, eye position, and similar viewing attributes. Many persons have difficulty with those adjustments. Additionally, static multi-focal lenses may be difficult to use in environments with objects at multiple distances positioned at similar viewing angles, for example, a car equipped with a GPS navigation screen.